IEEE 802.11 standards specify communication protocols for implementing wireless local area network (WLAN) communication between user equipments such as mobile phones, tablet computers and laptop computers, and network equipment such as access points. IEEE 802.11j standard introduces narrow bandwidth (e.g., 5 or 10 Mhz bandwidth) operation, or 802.11h standard also introduces narrow bandwidth (e.g., 1 Mhz bandwidth) operation, to achieve long range transmission up to 6 dB gain difference compared with popular 802.11 11b/g/n/ac standards using normal bandwidth (e.g., 20, 40, 80, or 160 Mhz).
In practice, during normal bandwidth operation, the network equipment may lose communication with the user equipment when the signal strength of the user equipment becomes weak because the user equipment has moved out of the signal coverage range of the normal bandwidth operation, or high packet error rate (PER) is detected due to packet collisions. Since the narrow bandwidth operation can achieve long range transmission up to 6 dB gain difference compared to the normal bandwidth operation, it is feasible to restore the communication between the network equipment and the user equipment by the narrow bandwidth operation.
However, there is no coexistence mechanism for narrow and normal bandwidth operations to allow station devices including user equipment and network equipment supporting both the narrow and normal bandwidths to communicate with each other using either narrow or normal bandwidth operation.